Why can't I bake any kind of functional normal map?
Switch from Blender 2.8 to 2.7 or 2.9, because 2.8 may be buggy with regard to baking.

Create a new image for the normal, enable the 32 bit Float option:




Your bake Extusion value is much too high, bring it back to 0.1 (or give your Ray Distance a value of 0.1):



In the Shader Editor, use a Normal Map node, not a Bump node.



Bake:


The low-res without the Normal map:

With the Normal map: